Redesign of Centrifugal Compressor Impeller by means of Scalloping

Abstract

Impellers of centrifugal compressors may experience resonance with vane passing frequencies, especially when operated away from the design conditions. Resonance can cause a serious structural damage to impeller. Complete redesign of an impeller to avoid resonance often requires major changes of the compressor stage design. This case study illustrates alternative approach to redesigning an impeller - scalloping of its coverplate and backplate. Scalloping changes impeller’s natural frequencies and allows achieving a separation margin from resonance, which is sufficient for reliable operation. At the same time, scalloping does not have a detrimental effect on impeller’s performances and allows to maintain existing configuration of compressor stage.